## C++, sort, insertion_sort.cpp

``````/**
*
* \file
* \brief [Insertion Sort Algorithm
* (Insertion Sort)](https://en.wikipedia.org/wiki/Insertion_sort)
*
* \details
* Insertion sort is a simple sorting algorithm that builds the final
* sorted array one at a time. It is much less efficient compared to
* other sorting algorithms like heap sort, merge sort or quick sort.
* However it has several advantages such as
* 1. Easy to implement
* 2. For small set of data it is quite efficient
* 3. More efficient that other Quadratic complexity algorithms like
*    Selection sort or bubble sort.
* 4. It's stable that is it does not change the relative order of
*    elements with equal keys
* 5. Works on hand means it can sort the array or list as it receives.
*
* It is based on the same idea that people use to sort the playing cards in
* their hands.
* the algorithms goes in the manner that we start iterating over the array
* of elements as soon as we find a unsorted element that is a misplaced
* element we place it at a sorted position.
*
* Example execution steps:
* 1. Suppose initially we have
* \f{bmatrix}{4 &3 &2 &5 &1\f}
* 2. We start traversing from 4 till we reach 1
* when we reach at 3 we find that it is misplaced so we take 3 and place
* it at a correct position thus the array will become
* \f{bmatrix}{3 &4 &2 &5 &1\f}
* 3. In the next iteration we are at 2 we find that this is also misplaced so
* we place it at the correct sorted position thus the array in this iteration
* becomes
* \f{bmatrix}{2 &3 &4 &5 &1\f}
* 4. We do not do anything with 5 and move on to the next iteration and
* select 1 which is misplaced and place it at correct position. Thus, we have
* \f{bmatrix}{1 &2 &3 &4 &5\f}
*/

#include <algorithm>
#include <cassert>
#include <iostream>
#include <vector>

/** \namespace sorting
* \brief Sorting algorithms
*/
namespace sorting {
/** \brief
* Insertion Sort Function
*
* @tparam T type of array
* @param [in,out] arr Array to be sorted
* @param n Size of Array
*/
template <typename T>
void insertionSort(T *arr, int n) {
for (int i = 1; i < n; i++) {
T temp = arr[i];
int j = i - 1;
while (j >= 0 && temp < arr[j]) {
arr[j + 1] = arr[j];
j--;
}
arr[j + 1] = temp;
}
}

/** Insertion Sort Function
*
* @tparam T type of array
* @param [in,out] arr pointer to array to be sorted
*/
template <typename T>
void insertionSort(std::vector<T> *arr) {
size_t n = arr->size();

for (size_t i = 1; i < n; i++) {
T temp = arr[0][i];
int32_t j = i - 1;
while (j >= 0 && temp < arr[0][j]) {
arr[0][j + 1] = arr[0][j];
j--;
}
arr[0][j + 1] = temp;
}
}

}  // namespace sorting

/**
* @brief Create a random array objecthelper function to create a random array
*
* @tparam T type of array
* @param arr array to fill (must be pre-allocated)
* @param N number of array elements
*/
template <typename T>
static void create_random_array(T *arr, int N) {
while (N--) {
double r = (std::rand() % 10000 - 5000) / 100.f;
arr[N] = static_cast<T>(r);
}
}

/** Test Cases to test algorithm */
void tests() {
int arr1[10] = {78, 34, 35, 6, 34, 56, 3, 56, 2, 4};
std::cout << "Test 1... ";
sorting::insertionSort(arr1, 10);
assert(std::is_sorted(arr1, arr1 + 10));
std::cout << "passed" << std::endl;

int arr2[5] = {5, -3, 7, -2, 1};
std::cout << "Test 2... ";
sorting::insertionSort(arr2, 5);
assert(std::is_sorted(arr2, arr2 + 5));
std::cout << "passed" << std::endl;

float arr3[5] = {5.6, -3.1, -3.0, -2.1, 1.8};
std::cout << "Test 3... ";
sorting::insertionSort(arr3, 5);
assert(std::is_sorted(arr3, arr3 + 5));
std::cout << "passed" << std::endl;

std::vector<float> arr4({5.6, -3.1, -3.0, -2.1, 1.8});
std::cout << "Test 4... ";
sorting::insertionSort(&arr4);
assert(std::is_sorted(std::begin(arr4), std::end(arr4)));
std::cout << "passed" << std::endl;

int arr5[50];
std::cout << "Test 5... ";
create_random_array(arr5, 50);
sorting::insertionSort(arr5, 50);
assert(std::is_sorted(arr5, arr5 + 50));
std::cout << "passed" << std::endl;

float arr6[50];
std::cout << "Test 6... ";
create_random_array(arr6, 50);
sorting::insertionSort(arr6, 50);
assert(std::is_sorted(arr6, arr6 + 50));
std::cout << "passed" << std::endl;
}

/** Main Function */
int main() {
/// Running predefined tests to test algorithm
tests();

/// For user insteraction
size_t n;
std::cout << "Enter the length of your array (0 to exit): ";
std::cin >> n;
if (n == 0) {
return 0;
}

int *arr = new int[n];
std::cout << "Enter any " << n << " Numbers for Unsorted Array : ";

for (int i = 0; i < n; i++) {
std::cin >> arr[i];
}

sorting::insertionSort(arr, n);

std::cout << "\nSorted Array : ";
for (int i = 0; i < n; i++) {
std::cout << arr[i] << " ";
}

std::cout << std::endl;
delete[] arr;
return 0;
}
``````